Polymeric chloroacylamides as gelatin hardeners



United States Patent Int. or. nine 1/30 US. Cl. 96-111 8 Claims ABSTRACT OF THE DISCLOSURE A process for hardening gelatin-containing layers characterized in that there is present at least one non-diffusing, polymeric chloroacylamide containing a recurring intralinear group of the formula R1 --CCH;-

Z-NH-C O-CHz-Cl wherein R is H or alkyl, e.g., methyl, and Z is a COCHR or CONH group where R is a phenylene nucleus or 1-6 methylene groups.

This invention relates to a process for hardening gelatin-containing photographic layers, especially silver halide emulsion layers.

It is known in the art that the mechanical strength of gelatin-containing photographic layers can be improved by adding hardening agents to such layers during their preparation. These hardening agents react chemically with the gelatin to form cross-linkages between individual polypeptide chains. The cross-linking reaction raises the melting point of the gelatin while at the same time the water absorption capacity or swelling capacity of the gelatin is diminished. Gelatin-containing layers, thus treated, have enhanced resistance to mechanical stresses and are resistant to treatment baths during processing. Conversely, unhardened layers swell a great deal in such baths and in the swollen state are extremely susceptible to mechanical injury. Since the melting point of gelatin is about 25-34 C. according to the degree of degradation, there is also the risk that unhardened gelatin-containing layers will soften and melt away entirely from the film support, especially if the processing is carried out at elevated temperatures.

Among the substances suggested as hardening agents are salts of metals, such as chromium and aluminum, aliphatic and aromatic aldehydes, dialdehydes, ketones, diketones, acid chlorides, halogenated acid amides, compounds having at least two ethylene oxide or ethyleneimine rings in the molecule, polyfunctional methanesulfonate esters, macromolecular polysaccharides containing secondary alcohol groups oxidizable to aldehyde groups and sulfurous acid adducts of polyacrolein.

In itself, the multiplicity of hardening agents known in the art indicates that hardening of gelatin-containing photographic layers is one of the most difficult problems in the production of photographic layers. Thus, nearly all of the hardening agents cited above have excellent capacity for hardening gelatin, but when they are introduced into photographic layers, especially in the photosensitive layer, serious disadvantages are usually encountered.

Some of these agents, such as formaldehyde in particular, exhibit an uncontrollable after-hardening action with its familiar untoward effects; in part also, some are not suificiently inert to the photosensitive silver halide emulsion and consequently cause a loss in sensitivity or impair gradation of the emulsion.

Again, other hardening agents so sharply diminish the swelling capacity of gelatin that the treatment processes are impaired because the processing baths cannot diffuse adequately into the layers. An additional disadvantage especially associated with the hardening agents of low molecular weight, is that they diffuse with relative ease into adjacent layers and there have an undesired hardening effect.

Now it has been found that polymeric chloroacylamide compounds having the general formula:

where:

R =H or alkyl Z=a carboxyamide group, having the structure:

or CO-NH-, where R =a phenylene nucleus or one or more methylene groups Y=H, a carboxyl group, or a COOR group wherein R is alkyl of l to 6 carbons, e.g., methyl, ethyl, propyl, butyl, amyl, hexyl, a phenyl group or a benzyl group n=a whole number from 0 to 5 m=a number designating the number of polymeric units; preferably this number is between 5 and 20, yet it may often even amount to 50 or more,

can be used to particular advantage for hardening gelatincontaining photographic layers, especially geIatino-silver halide emulsion layers. In contrast with the known hardening agents of low molecular weight, the polymeric compounds in accordance with this invention are distinguished by the fact that their molecular magnitude renders them fast to diffusion. Many of the hardening agents known in the art are known to have the disadvantage that they diffuse into adjacent layers and there react with certain emulsion additives, such as coupling agents, chemical or spectral sensitizers, stabilizers or other emulsion additives, and impair their eflicacy. Conversely, such diffusion is dependably excluded by use of the polymeric chloroacylamides in accordance with this invention. These emulsion additives retain their full efficacy, which is particularly important, especially in producing high-sensitive emul- SlOl'lS.

Another advantage associated wifh the diffusion-proof quality of these polymeric hardening agents is that in multilayers, individual layers of which contain the hardening agent in varied proportions, it is possible to adjust the various layers to a varied, defined degree of hardening and swelling; this can be accomplished only with difficulty with the more readily diffusible hardening agents of low molecular weight, since these exert an indefinite and difficulty controllable additional hardening effect by diffusion into adjacent layers.

While German Patent 1,156,649 discloses layer-confined hardening agents, the agents that are disclosed in this patent do not raise the melting point of the layers until during their treatment in alkaline baths. As may be seen readily, however, materials which are practically unhardened during storage are unsuitable for a great many purposes, e.g., for use in the tropics, or even if they are not stored under optimum conditions, since in these cases untoward effects may be expected which are due essentially to the undesirably low melting point of the gelatincontaining layers. For example, it has been found in practice that such layers, unhardened during storage, are susceptible to mechanical damage, especially during machine processing, sometimes coming into contact with the conveyor devices of the machines while still in an inadequately hardened condition.

Layers hardened with the compounds according to this invention are free from these drawbacks, because hardening has already reached its peak during storage. The polymeric compounds as described have high hardening power and their effect, calculated on the number of active groups for each molecular weight, is superior to that of the hischloroacylamides disclosed in German Patent 1,130,283.

comparatively small amounts of substance are required for achieving optimum hardening. The hardening action itself takes place rapidly and after application of the polymeric chloroacylamide hardening agent to the gelatin layer or coating. The hardening action reaches a peak value after only a short storage period. In no case could a deleterious after-hardening be observed. The polymeric hardening agents are also characterized by excellent compatibility with photosensitive silver halide emulsions and do not influence their sensitometer values in any way.

Other advantages are related to the polymeric structure of the compounds used in accordance with this invention. In compounds of the type disclosed here, reticulation is effected indirectly by way of the polymer chain, not directly by way of the active groups as in most hardening agents of low molecular weight. For this reason, the gelatin is cross-linked at greater intervals than in the close spaced cross-linking by hardening agents of low molecular weight. A result of this is that layers with improved permeability to processing baths are obtained.

This property advantageously distinguishes the hardening agents according to this invention from macromolecular oxidized polysaccharides, which because of their structure form reticulated products; products that inhibit diffusion of processing baths.

It has also been found that the drying time required for gelatin-containing layers hardened in accordance with this invention is sharply diminished, which is highly desirable, especially with respect to automatic processing. Presumably this phenomenon is due to the fact that in the use of the polymeric hardening agents of the type described herein, the hardening effect, proceeding by way of the predominantly hydrophobic polymer chains, lessens water retention.

Another advantage, related to the polymeric structure of the hardening agents used in accordance with this invention is that both the solubility and the hardening effect of the polymeric hardening agents can be varied over a wide range, depending on the particular comonomer and the amount used. Thus, they can be adapted to the widely varying requirements of the photographic art. In this connection a surprising observation was that when comonomers are employed which contain water-solubilizing groups, polymeric hardening agents are obtained which have excellent solubility in spite of their molecular weight, sometimes even more than of the comparable compounds of low molecular weight.

Finally, the type of cross-linking effected by the hardening agents according to this invention is also related to the fact that reticulation and hardening are effected with fewer active centers, calculated on the molecular weight, than in the hardening agents known in the art.

Compounds according to this invention can be employed for hardening photosensitive layers and likewise for hardening one or more gelatin-containing non-sensitive auxiliary layers, such as filter layers, antihalation layers, interlayers and antiabarasion layers.

Since the hardening agents used in accordance with this invention do not react with dye-coupling agents, they can be used with the best of results for hardening emulsions for color photography or gelatin-containing silver halide emulsions having incorporated therein at the same time color-forming agents. Insofar as they contain water-solubilizing groups in the molecule, the polymeric hardening agents are suitably added to the photographic layers in aqueous solution, e.g., sodium metaborate solution. In other cases, the addition can be effected by using solvents, aqueous mixtures, and if necessary, even solely with the use of organic solvents such as methanol, ethanol, glycol monomethyl ether, etc.

The amount of hardening agent to be added is adjusted according to the desired effect and can be readily ascertained and varied from case to case. In general, however, 0.13% of hardening agent, calculated on the dry weight of gelatin, will sutfice to impart adequate hardemng.

Since the polymeric hardening agents have no eifect on viscosity, they may be added to emulsions when ready for coating, at any desired time prior to coating.

The compounds perform their hardening function both in faintly acid and also in alkaline mediums. Whereas on the alkaline side the pH exerts no untoward influence, on the acid side there is advantage in not allowing pH to fall below 5.5.

If desired, the compounds according to this invention may also be used in combination with other hardening agents known in the art.

It should also be pointed out that photographic layers hardened with the substances here described have high stability of adhesion in the wet state, and effect excellent layer adhesion both in the wet and in the dry state.

From the large number of usable compounds of this type the following may be mentioned:

(1) Polymeric p-chloroacetylamino-N-rnethacrylanilide.

(2) Polymeric m-chloroacetylamino-N-rnethacrylanilide.

NH ONE-C OCHzCl ONE-C O-GHzCl (3) to (5) Copolymers from 1 and methacrylic acid.

(6) Polymeric N-chloroacetylmethacrylic acid hydrazide.

(7) Copolymer of l and hydroxyethyl methacrylate ester.

In these specific formulae, m has the same value as in the generic formulae above.

Preparation of the polymeric compounds may be illustrated with Compound 1 as an example.

The compounds according to this invention can be prepared in a variety of ways. For example, one simple possibility is starting with nitramine compounds such as pnitraniline (a) to make a polymerizable derivative (b) by reaction with chlorides of unsaturated acids, e.g., methacrylic acid chloride, this derivative forming by radicalwise polymerization and subsequent hydrogenation a polymer having reactive amino groups (d). The polymeric hardening agent can then be obtained by reacting the polymeric amine with chloroacetyl chloride.

Instead of a nitramino compound, e.g., nitraniline, diamines may be used initially, e.g., hydrazine hydrate, in which case the hydrogenation stage in the reaction sequence can be omitted. Polymerization of the polymerizable intermediates may be carried out not only as homopolymerization, but also as copolymerization with polymerizable vinyl compounds, e.g., methyl methacrylate, ethyl methacrylate, methacrylic acid, acrylic acid, acrylamide, methacrylamide, beta-hydroxyethyl methacrylate. In this way it is possible to vary the physical properties, e.g., the solubility, within a broad range and desired hardening action.

The examples below will explain the invention in greater detail, without limiting its scope in any way. Examples 1-3 pertain to the preparation, not claimed here, of the compounds to be used in accordance with the invention, while Examples 4-9 relate to their use in photographic materials.

Obviously, the compounds to be used in accordance with the invention can also be prepared by other processes or process stages known in the art.

PREPARATION-EXAMPLE l Poly-(p-chloroacetylamino-N-methacrylanilide) 1st Stage: p-Nitrornethacrylanilide.-A solution of 45 g. methacryl chloride in 30 ml. absolute dioxane is added dropwise to a solution of 55 g. p-nitraniline in a mixture of 90 ml. absolute pyridine and 90* ml. absolute dioxane, at 6080 C. while stirring. The reaction mixture is then stirred 2. hours at 100 C., cooled and poured into ice water/HCl. A nearly colorless precipitate forms; it is separated, washed with water and then dried. The product thus obtained is recrystallized from a little alcohol.

Yield 70 g.; melting point ISO-153 C.

2nd Stage: Poly-(p-nitromethacrylanilide).Stage I, 60 g., is dissolved in 600 ml. tert.butanol at C. and 2 g. azoisobutyrodinitrile is added as a catalyst. The mixture is then kept at the boiling point 2 hours in an atmosphere of nitrogen. This precipitates a pale yellow substance; after cooling, it is filtered ofi with suction, washed with ether and dried. The product is purified by treatment with ethanol. The yield is 32 g. of a faintly colored substance. Decomposition from 178 C.

3rd Stage: Poly-(p-aminomethacrylanilide).Atage II, 30 g., is dissolved in 300 ml. N-methylpyrrolidone, and reduced in an autoclave with Raney Ni/hydrogen (80 atm.) at 70 C. The solution obtained after removing the catalyst proceeds directly to further processing.

4th Stage: Poly-(p-chloroacetylamino-N-methacrylanilide.Chloroacetyl chloride, 22 g., is added dropwise at 0 C. to 300 ml. of the N-methylpyrrolidone solution (Stage III), obtained as above. After stirring for a short time, 300 ml. water is added at 05 C. The mixture is adjusted to neutrality with 10% NaOH, stirred, filtered from the precipitate which forms, and the precipitate is washed with water. For additional purification the product is treated with alcohol.

Yield 24 g.; decomposition above 250 0.; analysis: N, 11.7%, C1, 12.7%.

PREPARATIONEXAMPLE 2 Copolymer from the monomer of Preparation-Example 1 and methacrylic acid 1st Stage.-Like State I in Preparation- Example 1.

2nd Stage-Stage I product, 100 g., and 66 g. of pure methacrylic acid were dissolved in 1000 ml. tert.-butanol at C. To the resulting solution 8 g. azoisobutyrodinitrile was added, with stirring, and stirring was continued 2 hours at a gentle boil. After cooling, the reaction mixture was stirred into 4 liters of ether, and the mixture was allowed to stand 10 hours at room temperature. The resulting pale precipitate was filtered OE With suction, washed several times with ether and then dried. For purification it was digested with alcohol. The copolymer is soluble in dilute NaOI-I to a clear yellow solution.

Yield 142 g.; Melting point 222-229 C.

3rd Stage.-Reduction of Stage II was performed as described in PreparationExample 1, Stage III.

4th Stage-The preparation is analogous to Stage IV of PreparationExample l. A nearly colorless substance was obtained, which dissolved smoothly in a. sodium metaborate solution.

Yield: 130 g. from 142 g. of Stage II; the substance decomposes from 210 C.

PREPARATION-EXAMPLE 3 Z-chloroacetylhydrazide of polymethacrylic acid 1st Stage: Polymethacryl chloride.By reacting polymethacrylic acid with thionyl chloride.

2nd Stage: Polymethacryl hydrazide.-A reaction flask is charged with 60 ml. of 80% hydrazine hydrate, mixed with 60 ml. of dimethylformamide. Into this is added a solution of 23 g. polymethacryl chloride (Stage I) dissolved in 100 ml. dimethylformamide. A colorless precipitate is formed, with a rise in temperature. After 12 hours, the precipitate is separated, washed with methanol and dried.

Yield: 23 g.

3rd Stage: 2-Chloroacetylhydrazide of polymethacrylic acid-Stage II, 23 g., is dissolved in 600 ml. distilled water at 30 C. and the solution is cooled to C. At 05 C. 60 g. of chloroacetyl chloride is added dropwise; this forms a colorless precipitate, After continuing the stirring for a short time, the pH is adjusted to 7 by adding 2 N NaOH, the solid component is filtered off with suction, washed with Water and dried.

Yield 19 g.; Decomposition point 190 C.;

Analysis.N, 18.01%.

Application Examples:

EXAMPLE 4 To 1 liter of gelatin solution, containing 50 g. of dry gelatin, there is added 1.5 g. of Compound 7, dissolved in a mixture of glycol monomethyl ether and ethanol. The solution is coated on a prepared cellulose acetate film support and this is dried. After 3 days of storage at 50 C. the layer has a melting point above 100 C., very little swelling, and good adherence in the wet state to the support.

EXAMPLE 5 To 1 kg. of a silver bromide emulsion, ready for coating and containing about 88 g. gelatin, there is added 1.6 g. of Compound 1, dissolved in a mixture of ethylene glycol monomethyl ether and ethanol. The emulsion is cast on a prepared film support. After drying and storing 3 days at 50 C., a layer is obtained which has a melting point above 100' C., little swelling, good adherence and good stability of grip in the wet state. The photographic properties of the silver halide emulsion layer are practically unchanged.

EXAMPLE 6 To 1 liter of a gelatin solution, containing 50 g. dry gelatin and 5 ml. of a dye solution, forming a filter layer, there is added 1.5 g. of Compound 5, dissolved in a mixture of ethylene glycol monomethyl ether and ethanol. After drying and storing for 1 week, the layer has a melting point above 100 C. Swelling of the layer is slight, adherence is good.

EXAMPLE 7 To 1 kg. of a spectrally sensitized silver bromide emulsion, ready for coating and containing 88 g. dry gelatin, 5% AgBr and 10 g. of the dye-coupling agent l-sulfophenyl-3-stearoyl-5-pyrazolone there is added 1.3 g. of Compound 1 dissolved in a mixture of glycol monomethyl ether and ethanol; this emulsion is cast on a prepared film support and dried. After 5 days of warm storage at 50 C., it had reached a melting point above 100 C. Small swelling and good adhesion were achieved. No loss in color density occurred during storage. The table below gives information about the hardening effect:

Melting point after storing 5 days at 50 C.Amount of hardening agent, calculated on dry gelatin:

Percent C. 0 34 0.5 75 1 above 100 1.5 above 100 EXAMPLE 8 To 1 liter of a gelatin solution containing 25 g. of gelatin and forming a protective layer, there is added 0.8 g. of Compound 5, dissolved in an aqueous sodium metaborate solution at pH 7.1. The solution is cast on a layer carried on film support, After drying and subsequent storage for 2 days at 50 C., a well hardened protective layer is obtained, which has excellent adhesion in the wet state.

EXAMPLE 9 Fogging values for a high-sensitivity x-ray film material, hardened with various hardening agents, added only after coating the upper layer.

Fogging Fogging value after value aiter developing developing Hardening agent; type 3 minutes 8 minutes Polychloroacylamide from preparation, ex-

am e 0. 08 0. 17 Polyehloroac mi fr preparation, ex

am 01-. 0.25 0.36 Bis-ethyleneirnlno compound according to German Patent Application I 72, 895 IVaI 57b 0. 54 0. Bis-epoxy compound according to German Patent 1,095,113 Above 1.00 Above 1.00 Bis-sult'onylethyleneimine compound according to U.S.P. 2,964,404 Above 1.00 Above 1.00 Bis-chloroacylamlde according to Ge man Patent 1,130,238 Above 1.00 Above 1.00 Bis-chloroacyl ester according to U Above 1.00

2,732,303 Above 1.00

l lmlllcmll i u 1 ii.

III.

wherein R is H or alkyl,

Z is a COCHR or -CO--NH group where R; is a phenylene nucleus or 1 to 6 methylene groups, Y is COOH or COOR where R is alkyl of 1 to 6 carbon atoms, a phenyl nucleus or a benzyl group, n is a cardinal number from 0 to 5, and m is at least 5.

2. A process according to claim 1 where m is 5-20.

3. A process according to claim 1 wherein the polymeric chloroacylamide is added in an amount of 0.1% to 3.0% by weight based on the dry weight of the gelatin in said layer.

4. A process according to claim 1 wherein said layer is a gelatinO-silVer halide emulsion layer of a photographic film or paper element.

9 10 5. A process according to claim 1 wherein said layer References Cited is a gelatino-silver halide emulsion layer containing a dif- FOREIGN PATENTS fusionproof color former.

6. A process according to claim 1 wherein said poly- 1,305,988 9/1962 Francemeric chloroacylamlde 1s polymeric p-chloroacetylaminm 5 NORMAN G- TORCHIN, Primary Examiner.

N-methacrylanilide.

7, A photographic element bearing at least one gelatin- 1. R. EVERETT, Assistant Examiner. containing layer hardened by means of at least one polymeric chloroacrylamide as defined in claim 1. U.S. Cl. X.R.

8. A process according to claim 1, wherein R is 10 96 1 14 CH 

